CS 350, slide set 5
M. Overstreet
Old Dominion University
Fall 2004
Reading
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PSP text, ch. 11, 12, 13, 14
Topics
A software development process
Measuring software quality
„ Finding defects
„ A code review checklist
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1
Process
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A sequence of steps to complete a
task
Provides guidance
Can provide a record of what has been
accomplished
„ Can provide an indication of percent of
project which has been completed
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• After we’ve used 50% of time allocated,
have we finished 50% of the work?
Some basic definitions
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Recall defn’s from Ch. 5
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Project: produces a product
Task: an element of work
Process: the steps to produce a product
Plans: the way a specific project is to be done; how,
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Job: something you do; either a project or a task
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Product: something you produce, usually for
someone else
when, at what costs
More
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Processes can have various phases
Each phase can consist of several activities
PSP process
Requirements
Planning
Plan data
Code Design
Test Design
Scripts
Guidance
Logs
Code
Project
plan
summary
Compile
Test
Post Mortem
Time and
defect data
Finished product
Actual
data
Plan and actual
project and process
data
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PSP process script - 1
Purpose
To guide you in developing programs
Entry
Criteria
Problem statement
PSP Project Plan Summary form
Actual size and time data from old projects
Time Recording Log
1
Planning
Identify program functions
New!
Identify test objectives
Estimate max, min, and total LOC
Determine minutes/LOC
Calculate max, min, and total time
Enter data in Project Plan Summary Form
Record planning time in Time Recording Log
2
Code
design
Design the program
Record design in specified format
Enter code design time in Time Recording Log
3
Test
design
Prepare test plans and data
Enter test design time in Time Recording log
New!
PSP Process Script - 2
3
Code
Implement the design
New!
Complete a Makefile
Use a standard format for entering code
Record coding time in Time Recording Log
4
Compile
Compile the code
Fix defects as discovered
Record time in Time Recording Log
5
Test
Test the program
Fix defects as discovered
Complete test reports
Record time in Time Recording Log
6
New!
Postmortem
Complete the Project Plans Summary with actual
time and size data
Record postmortem time in Time Recording Log
Exit criteria
A thoroughly tested program
A properly documented design
Complete source code
Documented and corrected test data
A Makefile
A completed set of test reports
A completed Project Plan Summary
Completed Time Logs; All required submitted.
New!
Project Plan Summary
Example
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See word doc on web:
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Forms area of 350 material, planning &
final.
Detailed, step-by-step, instructions:
text, Table 11.3 (pg. 129)
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Announcements
Exam 1 next week.
„ Covers PSP text.
„ Covers overview of GCS spec.
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Will be take home.
„ Open book, open notes
„ Designed to take 1 hour to complete
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Software Quality
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Complex topic
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Includes, among many possibilities:
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How do customers measure the quality of a product?
How do developers measure the quality of a product?
How many problems does a typical user encounter
when using the product?
Does the product provide key functionalities to the
user?
How do features of this product compare with
competing products?
How easy is it to enhance/modify/extend/revise/tailor
the product?
How easily can components from this product be used
in other products?
We’re going to keep it simple: defects/KLOC
What’s a defect in PSP?
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Anything wrong with a program:
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Misspelling in comment
Bad punctuation, poor formatting
Incorrect logic
Missing functionality
Documentation, format does not conform to
organizational standard
In short, any change you make to code
after you type it in and proofread it.
Errors are mistakes people make. Some
result in defects in code.
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Defect types
Type
Number
10
Type Name
Description
Documentation comments, messages
20
Syntax
spelling, punctuation, typos, instruction formats
30
Build, package
change management, library, version control
40
Assignment
declaration, duplicate names, scope, limits
50
Interface
procedure calls and references, I/O, user formats
60
Checking
error messages, inadequate checks
70
Data
structure, content
80
Function
logic, pointers, loops, recursion, computation, function
defects
90
System
configuration, timing, memory
Environment
design, compile, test, other support system problems
100
Why record defect types?
To have real data on what is causing
problems
„ To help direct possible changes to
software processes
„ Pointless unless defect types,
frequencies, and times-to-fix are
periodically analyzed and acted upon
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Goals of defect form
Improve your programming
Reduce number of defects in your
code
„ Save you time
„ To do you job responsibly: you find
your own mistakes rather than
someone else finding them
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Defect log
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See web for forms and example
See instructions, table 12.3, pg. 145
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Inject: in which step was defect inserted?
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Remove: in which step was defect detected?
• Guess if you need to.
• Eventually, we want to know when’s the most
efficient time to find defects.
• Need data for this.
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Fix defect: did this defect come from a “too
quick” fix of another defect? If so, which one?
• Guess if you need to.
Fixing defects
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Recognize defect symptoms
From symptoms, deduce likely locations
of defects
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Sometimes hard to do, sometimes not
Identify source
Fix it
Verify that the fix:
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Resolved the problem
Did not introduce new problems
Ways to find code defects
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Let others find them (not recommended)
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Use testing to locate defects
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Use mathematical methods (proofs of
correctness) to locate defects
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This approach has some disadvantages
Widely used; very expensive; misses many
Rarely used; very expensive, maybe infeasible
in most cases
Use Code Reviews
Use Code Inspections (will discuss later)
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Why Code Reviews?
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Compilers miss lots of typo/syntax errors
(probably 10% -- depends on language)
Testing misses lots of defects (some
assert 50%)
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No matter how many defects are in the code
to begin with!
Testing and code reviews are probably
complimentary activities
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Code reviews can find some defects not easily
found in testing
Testing finds can some defects not easily
found by code reviews
Review before compiling!
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Takes as long to do review before as after
Saves some compile time
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Typically 10% to 15% if done without review
Typically ~3% if done with review
Compiles finds errors equally well with or
without review
Reviewers don’t find errors as effectively
if they know the code has compiled
cleanly. Probably human nature:
• if we don’t really expect to find things, we don’t look
as hard.
• if we expect to find things and don’t, we probably
look again.
Additional comments
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In PSP, you do your own reviews.
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Goal is to save you time, improve your code
quality
In TSP (remember the next textbook?),
this is supplemented by inspections.
Since fixing code is so expensive, we
have much industrial data that shows
reviews pay!
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Code review script - 1
Entry criteria
Check that the following are on hand:
1. The requirements statement
2. The program design
3. The program source code
4. The coding standards
5. A Defect Recording Log
1
Review procedure
First produce the finished program source code.
Before compiling, print a source listing
Next, do the code review
During the code review, carefully check every line of source
code to find and fix as many defects as possible
2
Fix the defects
Fix all defects found
Check the fixes to ensure they are correct
Record the defects in the Defect Recording Log
3
Review for
coverage
Verify that the program design fulfills all of the functionality
described in the requirements
Verify that the source code implements the design
Code Review Script - 2
4
Review the program Verify that the design logic is correct
logic
Verify that the source code correctly implements the
design logic
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Check names and
types
Verify that all names and types are correctly declared and
used
Check for proper declaration of integer, long int., and
floating point data types
6
Check all variables
Ensure that every variable is initialized
Check for overflow, underflow, and out-or-range
problems
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Check program
syntax
Verify that the source code properly follows the language
specifications
Exit criteria
At completion you must have:
1 The completed and corrected source code
2. Completed Time Recording Log
3. Completed Defect Recording Log
Code Review Checklist
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See text, table 14.1, pg. 177
Use different checklists for different
languages
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Different languages have different short
comings
• While some mistakes are common-place in many
languages, features of a particular language often
cause people to make similar mistakes
• Your checklist should evolve and be based on what
you discover about your own behavior from your
own code reviews!
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C++ Coding Standard
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See text, Table 14.9, pg. 189
Starting with assignment 4, this is what
the grader will use for future
assignments.
Follow formatting rules.
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Some editors automatically indent. Take
advantage of this.
Grading rules:
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Any submitted code that does not fully comply
with the coding standard from the text will not
be graded.
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